When New York Giants wide receiver Victor Cruz sprinted past two members of the Washington Redskins’ secondary Sunday and hauled in a game-winning, 77-yard touchdown pass from quarterback Eli Manning, it dramatically changed the Washington Redskins’ outlook as they near the halfway point of the season.

Instead of celebrating more late-game exploits by rookie quarterback Robert Griffin III and admiring the view from the perch of a first-place tie in the NFC East, the Redskins are back in last place, staring up at the rest of the division with a record of 3-4 entering another challenging game this weekend at Pittsburgh. And they’re still searching desperately for ways to fix a pass defense that ranks last in the NFL.

“It hurts and it was definitely crazy,” defensive tackle Barry Cofield said of the Manning-to-Cruz touchdown in the Redskins’ locker room late Sunday afternoon. “It’s just such a helpless feeling for a [defensive] lineman when the ball is in the air. It’s just in the air and all you can do is watch it.”

The Redskins have been virtually helpless all season against opponents’ passing games, a shortcoming that is threatening to undermine all the good accomplished by Griffin and Washington’s highly productive offense. The Redskins are yielding an NFL-worst 328.4 passing yards per game. Only two other NFL teams, the New Orleans Saints and Tampa Bay Buccaneers, are surrendering more than 290 passing yards per outing.

The NFL is, more than ever, a pass-first league, and opposing quarterbacks have used that weapon to full advantage against the Redskins. Manning threw for 337 yards on Sunday. The Redskins have held only one opposing quarterback below 300 passing yards this season. That was the Buccaneers’ Josh Freeman, who threw for 299 yards.

“Talent-wise, they’re not very good,” one former NFL front-office personnel man said Tuesday, speaking on the condition of anonymity to offer a frank assessment of the Redskins’ pass defense.

“In fairness to them, they’re playing with two backup safeties. [Brandon] Meriweather and Tanard Jackson are not there. The guys who are playing instead of them are not that good. . . . They’ve got guys that can’t run. There’s not a lot of speed. At corner, DeAngelo Hall is a highlight-reel guy but he’s not consistent. The other guys they’ve got at corner are just guys. They’re average.”

Meriweather hasn’t played all season because of a knee injury. Jackson is serving a suspension of at least a year for violating the NFL’s substance abuse policy. Madieu Williams and Reed Doughty started at the safety spots Sunday.

Cruz ran past cornerback Josh Wilson and Williams on his decisive touchdown. The personnel man said Williams was at fault because a safety must keep a receiver in front of him, especially late in a game while protecting a lead.

“Madieu Williams is a pretty instinctive player,” the personnel man said. “That’s what was really surprising about what happened the other day. He’s made some good plays for them. That was not one of them, obviously.”

The former personnel man said he doesn’t consider defensive coordinator Jim Haslett and secondary coach Raheem Morris, the former Buccaneers head coach, primarily responsible.

“You have a little bit of the mad scientist element, where you can devise a game plan to shut down the best offense in the league but you leave yourself open to all these big plays,” he said. “There is a bit of that. But I’m sure they’d tell you they have to play that way because of the talent they have.”

Redskins Coach Mike Shanahan defended his assistants Monday. When asked during his news conference whether the pass defense struggles are attributable in part to an adjustment period with Morris, Shanahan said no.

“You take a look at that one play for a 77-yard big play, everybody is sick about it,” Shanahan said Monday. “All of a sudden, if we play it like we normally play it, we play a pretty good game. We got a couple turnovers. We get a sack. We hit Eli a number of times during the game where he hasn’t normally been hit that many times. Then all of a sudden when you do give up that big play, it takes all of the good things that we did on defense. Instead of having 260 yards passing, you’ve got 340. You’ve got the play of the game. It negates all the good things.”

Shanahan declined to assess blame or discuss the specifics of what happened on the Cruz touchdown. He said the Redskins are “pretty tough on ourselves” and will work to improve what needs to be fixed. He mentioned a list of losses on defense that also includes the season-ending injuries to outside linebacker Brian Orakpo and defensive end Adam Carriker, two of their better pass rushers.

“Different guys are playing different positions,” Shanahan said. “And it doesn’t happen just like that. Sometimes there is a break in a coverage or a guy not aligned properly or maybe the stats aren’t quite the same as they were a year ago. But we’re going to keep on working to try to fill some of those holes. And hopefully guys that fill those voids can step up and play at a high level.”

The Redskins do have 10 interceptions, tied for third in the league, and have returned three of them for touchdowns. But without Orakpo and Carriker, they have a relatively modest 13 sacks, which ties them for 18th in the league. Cofield said the defensive front must do its part against the pass.

“We’ve got to get there faster,” Cofield said. “We had some hits. I wouldn’t say that Eli enjoyed himself today. I don’t think he felt like he had all day. But we didn’t get there soon enough. We’ve got to get some sacks, force some fumbles, whatever it takes to limit these passing yards.”

Notes: The Redskins re-signed running back Keiland Williams and cut seldom-used backup RB Ryan Grant. The team also signed cornerback Domonique Johnson to the practice squad and waived wide receiver Emmanuel Arceneaux.